Generally speaking, a radio wave is an electromagnetic wave propagated by an antenna. Radio waves can have different frequencies. Tuning a receiver to a specific frequency allows the receiver to pick up or listen to the waves or signals propagated at that specific frequency.
In the United States, the Federal Communications Commission (the FCC) governs which frequencies may be used and for what purposes. In effect, the FCC has divided the radio frequencies into frequency bands or spectrums and issues licenses to entities desiring to use those frequency bands.
Common frequency bands include the following: AM radio—535 kilohertz (KHz) to 1.7 megahertz (MHz); Short wave radio—bands from 5.9 MHz to 26.1 MHz; Citizens band (CB) radio—26.96 MHz to 27.41 MHz; FM radio—88 MHz to 108 MHz; and Television stations—174 to 220 MHz for channels 7 through 13.
Though there are some unlicensed spectrums, many wireless devices have their own band. Garage door openers operate around 40 MHz. Baby monitors operate around 49 MHz. Many relatively simple radio controlled (RC) toys operate at either 27 MHz or 49 MHz, which represent frequencies allocated by the FCC for basic consumer items. Advanced RC models, such as the more sophisticated RC airplanes and RC cars may use 72-MHz or 75-MHz frequencies, respectively.